    [Relevant reference 1] Korean patent registration number 0041791, May 15, 1991    [Relevant reference 2] Korean patent registration number 0210368, Apr. 26, 1999
Conventional motors are driven by fossil energy such as gasoline, coal, gas, etc. the reciprocation movement of a piston of which generated by means of explosion is converted into a rotational movement via a crank.
However, the fossil energy source runs out because the amount of fossil energy is very limited in nature and serves to contaminate environment when in use.